Abstract: To delay the onset of stall conditions at the tips of the blading an of axial-flow, mixed-flow and axial-centrifugal compressors, at the tips of the annular arrays of blading anti-stall tip treatment arrangement is provided at least at one of the arrays (2) comprising an annular cavity (3) communicating with the flow path through the compressor through slots (5) formed by an annular grid of ribs (4). The slots (5) provide communication between the cavity (3) and the flow path (7, 8) both upstream of and axially coincident with the array of blades (2). The ribs (4) are inclined relative to the radial direction at an angle (.phi..sub.r) of b 30.degree. to 50.degree.. The pitch (t) of the ribs and the slot width (.delta..sub.s) between the ribs are in the ratio of 1.5 to 2.0. The rib radial projection height (h) and the slot width are in the ratio of 1.1 to 1.8. The axial length (L) of the grating of ribs and the blade tip chord axial projection (b') of the array of blades (2) are in the ratio of 0.5 to 1.5.